Definition
The Energy Information Administration (EIA) provides weekly information on natural gas stocks in underground storage for the U.S. and five regions of the country. The level of inventories helps determine prices for natural gas products.

Why Investors Care
Natural gas product prices are determined by supply and demand - just like any other good and service. During periods of strong economic growth, one would expect demand to be robust. If inventories are low, this may lead to increases in natural gas prices. If inventories are high and rising in a period of strong demand, prices may not need to increase at all, or as much. During a period of sluggish economic activity, demand for natural gas may not be as strong. If inventories are rising, this may push down natural gas prices.